.woocommerce span.onsale {
    background-color: #d32f2f;
    color: #ffffff;
    font-size: 16px;
    font-weight: bold;

    width: 70px;
    height: 70px;

    display: flex;
    align-items: center;      /* verticaal centreren */
    justify-content: center;  /* horizontaal centreren */

    border-radius: 50%;
    text-transform: uppercase;
    box-shadow: 0 4px 10px rgba(0,0,0,0.3);
}